The invention relates to a heat storage means, more especially a latent heat storage means for motor vehicle heating means supplied with engine waste heat, comprising an inner housing surrounding a storage core, an outer housing surrounding the inner housing with a clearance and an evacuated load bearing thermal insulation means between the inner housing and the outer housing.
It is also known practice to evacuate the space between an inner and outer housing as a vacuum space so that if the space is in the form of a narrow gap there is a powerful insulating effect. In this respect it is also a known practice to fill such a gap prior to evacuation with a microporous material, which serves to support the outer housing on the inner housing and thus to take up the force due to the vacuum so that the outer housing may be made with a comparatively thin wall in order to reduce weight and costs.
In order to create a highly efficient insulation it is convenient to produce a high vacuum in the vacuum gap. In order to maintain such a high vacuum over a long period of time it is necessary to degas the surface layers next to the vacuum gap of the inner and outer housings. Both the evacuation and the degassing operation as well are hindered by the high resistance to flow of the load bearing insulation of microporous materials.
The highly efficient insulation strived for by having a high vacuum is impaired to a certain extent by the solid state conduction, caused by the load bearing insulation, between the inner and the outer housings.